Provide a mechanism for providing the carcinogenesis research community with a source of documented reference samples of carcinogens and related compounds. Although some of the compounds stocked are commercially available, supplies are undependable in many cases and in other cases, material of adequate purity is difficult to obtain. Many of the compounds needed, such as the PAH metabolites and nitrosamines, must be synthesized by other NCI contractors. The repository is responsible for the secure storage, repackaging, and distribution of samples of these compounds with analytical documentation and safe handling recommendations.